Trace metal elements: a bridge between host and intestinal microorganisms

Trace metal elements, such as iron, copper, manganese, and zinc, are essential nutrients for biological processes. Although their intake demand is low, they play a crucial role in cell homeostasis as the cofactors of various enzymes. Symbiotic intestinal microorganisms compete with their host for the use of trace metal elements. Moreover, the metabolic processes of trace metal elements in the host and microorganisms affect the organism's health. Supplementation or the lack of trace metal elements in the host can change the intestinal microbial community structure and function. Functional changes in symbiotic microorganisms can affect the host's metabolism of trace metal elements. In this review, we discuss the absorption and transport processes of trace metal elements in the host and symbiotic microorganisms and the effects of dynamic changes in the levels of trace metal elements on the intestinal microbial community structure. We also highlight the participation of trace metal elements as enzyme cofactors in the host immune process. Our findings indicate that the host uses metal nutrition immunity or metal poisoning to resist pathogens and improve immunity.

Rheb promotes brown fat thermogenesis by Notch-dependent activation of the PKA signaling pathway

Increasing brown and beige fat thermogenesis have an anti-obesity effect and thus great metabolic benefits.However,the molecular mechanisms regulating brown and beige fat thermogenesis remain to be further elucidated.We recently found that fat-specific knockout of Rheb promoted beige fat thermogenesis.In the current study,we show that Rheb has distinct effects on thermogenic gene expression in brown and beige fat.Fat-specific knockout of Rheb decreased protein kinase A(PKA)activity and thermogenic gene expression in brown adipose tissue of high-fat diet-fed mice.On the other hand,overexpression of Rheb activated PKA and increased uncoupling protein 1 expression in brown adipocytes.Mechanistically,Rheb overexpression in brown adipocytes increased Notch expression,leading to disassociation of the regulatory subunit from the catalytic subunit of PKA and subsequent PKA activation.Our study demonstrates that Rheb,by selectively modulating thermogenic gene expression in brown and beige adipose tissues,plays an important role in regulating energy homeostasis.